# std::flat_map<Key,T,Compare,KeyContainer,MappedContainer>::insert_range

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< cpp‎ | container‎ | flat map

template< container-compatible-range<value_type> R > void insert_range( R&& rg ); |  | (since C++23)

Inserts a copy of each element in the range rg into underlying containers `c` as if by:

    for (const auto& e : rg)
    {
        c.keys.insert(c.keys.end(), e.first);
        c.values.insert(c.values.end(), e.second);
    }

Then, sorts the range of newly inserted elements with respect to value_comp(). Merges the resulting sorted range and the sorted range of pre-existing elements into a single sorted range. Finally, erases the duplicate elements as if by:

    auto zv = views::zip(c.keys, c.values);
    auto it = ranges::unique(zv, key_equiv(compare)).begin();
    auto dist = std::distance(zv.begin(), it);
    c.keys.erase(c.keys.begin() + dist, c.keys.end());
    c.values.erase(c.values.begin() + dist, c.values.end());

Each iterator in the range rg is dereferenced exactly once. The behavior is undefined if rg overlaps with the container.

| Information on iterator invalidation is copied from here

### Parameters

rg | - | a container compatible range, that is, an `input_range` whose elements are convertible to `T`

### Return value

(none)

### Complexity

N + M·log(M), where `N` is size() before the operation and `M` is ranges::distance(rg).

### Notes

Since `insert_range` performs an in-place merge operation, that may allocate memory.

### Example

Run this code

    #include <iostream>
    #include <flat_map>
    #include <utility>

    void println(auto, auto const& container)
    {
        for (const auto& [key, value] : container)
            std::cout << '{' << key << ',' << value << '}' << ' ';
        std::cout << '\n';
    }

    int main()
    {
        auto container = std::flat_map{std::pair{1, 11}, {3, 33}, {2, 22}, {4, 44}};
        const auto rg = {std::pair{-1, -11}, {3, -33}, {-2, -22}};
    #ifdef __cpp_lib_containers_ranges
        container.insert_range(rg);
    #else
        container.insert(rg.begin(), rg.end());
    #endif
        println("{}", container);
    }

Output:

    {-2,-22} {-1,-11} {1,11} {2,22} {3,33} {4,44}

### See also

insert | inserts elements (public member function)

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